Various horizontal beam antennas have been known which function primarily as directional antennas. With the increasing use of radio transmitting and receiving apparatus, the frequency spectrum has become increasingly congested, and it has become desirable to switch between horizontal and vertical mode of operation to avoid congestion when possible. Furthermore, with the increasing use of mobile radio units, the majority of which use vertically polarized antennas, it has become desirable to have the facility for vertical mode operation to allow effective communication with mobile units.
One attempt to provide a dual polarity directional antenna has been the provision of a quad antenna having a reflector loop and a single driven loop wherein conductive cross-arms are utilized together with an electrical network to drive the quad loop in either the vertical or horizontal mode. However, the additional electrical network required to obtain dual polarity increases the cost of having such capability as well as the complexity of the unit. Further, due to the arrangement of the quad antenna in four equal legs, the signals arrive out of phase at the central determination point reducing its effectiveness.
U.S. Pat. No. 3,284,801 discloses a large loop beam antenna wherein the loops are constructed of a plurality of tubular metallic sections which are sprung into a curved shape and fastened end to end. However, such are susceptible to being bent during shipping and handling resulting in loss in structural integrity. Non-conducting material is required to reinforce and support the loop configuration.